At present, there are mainly two steel smelting methods worldwide, 60-70% of which is the converter steel smelting with a long process flow, and the other is the electric furnace (also referred to as the electric furnace steel smelting process) with a short process flow. The main raw materials for the electric furnace smelting process are the scrap steel, and most of the industrial or municipal scrap steels are lightweight and thin sheets, with a low content of carbon (0.10˜0.35%). Moreover, due to long-term storage in open air, most of the scrap steels have the surface rust, such that when smelting the scrap steels in the electric furnace, the carbon must be added in the charge depending on the requirements of carbon content for steel smelting. During the preparation of carbon, considering the fact that some carbon is fire lost and part of carbon must be also used in the reduction reaction with Fe2O3, the amount of carbon make-up is very high. Usually, the materials for adding the carbon include the pig iron, melted iron, blocky coke, waste graphite electrode or carbon-containing pellet, and the powdery carbonaceous materials are blown into the melted steel.
In the prior art, the carburetion additive for electric furnace smelting is materials with a carbon content more than 80%, including the common carbon-containing pellet etc, in addition to the molten iron or pig iron. For example, Japan Patent No. 3750928, (Application No. 2001-373378 filed on Dec. 8, 2001) disclosed a carburetion additive comprising 20-80% of lime-based materials and 20-80% of carbonaceous materials, and a steel smelting method. However, this additive can't be kept in open air for long period while keeping its performances, and it may be usually stored in open air for less than 7 days.